The invention relates to semiconductor devices and, in particular, to a vertical DMOS Transistor.
Lateral double-diffused metal-oxide-semiconductor (LDMOS) transistors are commonly used in high-voltage applications (less than 10V to >1000 volts) because of their high breakdown voltage characteristics and compatibility with CMOS technology for low voltage devices. FIG. 1 is a cross-sectional view of a conventional low-side N-type LDMOS transistor. It is well known that by increasing the length of the drift region, denoted by the distance “d”, the breakdown voltage of the LDMOS transistor can be accordingly increased.
FIG. 2 is a cross-sectional view of a conventional trench MOSFET device. In a trench MOSFET device, the gate electrode is formed in a trench and the channel is formed in a vertical region along the sidewall of the trench. The trench MOSFET device is thus a vertical transistor device with the source region on the top side and the drain terminal on the back side of the device. U.S. Pat. No. 7,576,391, to Williams et al., also describes a lateral trench MOSFET device with a trench gate to control channel current vertically down the side of an etched trench.